virtio_mmio: Return early if no device

If there is no device, don't write to any registers.

ok jan@

diff --git a/sys/dev/fdt/virtio_mmio.c b/sys/dev/fdt/virtio_mmio.c
index 5c28547..c88d58e 100644 (file)
--- a/sys/dev/fdt/virtio_mmio.c
+++ b/sys/dev/fdt/virtio_mmio.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: virtio_mmio.c,v 1.13 2024/05/17 16:37:10 sf Exp $     */
+/*     $OpenBSD: virtio_mmio.c,v 1.14 2024/08/20 07:04:29 sf Exp $     */
 /*     $NetBSD: virtio.c,v 1.3 2011/11/02 23:05:52 njoly Exp $ */
 
 /*
@@ -271,16 +271,16 @@ virtio_mmio_attach(struct device *parent, struct device *self, void *aux)
        id = bus_space_read_4(sc->sc_iot, sc->sc_ioh, VIRTIO_MMIO_DEVICE_ID);
        printf(": Virtio %s Device", virtio_device_string(id));
 
-       if (sc->sc_version == 1)
-               bus_space_write_4(sc->sc_iot, sc->sc_ioh,
-                   VIRTIO_MMIO_GUEST_PAGE_SIZE, PAGE_SIZE);
-
        printf("\n");
 
        /* No device connected. */
        if (id == 0)
                return;
 
+       if (sc->sc_version == 1)
+               bus_space_write_4(sc->sc_iot, sc->sc_ioh,
+                   VIRTIO_MMIO_GUEST_PAGE_SIZE, PAGE_SIZE);
+
        vsc->sc_ops = &virtio_mmio_ops;
        vsc->sc_dmat = sc->sc_dmat;
        sc->sc_config_offset = VIRTIO_MMIO_CONFIG;